In telephony an equalizer is used on a subscriber line circuit to compensate for losses in transmission by providing frequency selective attenuation. A commonly used equalizer is an analog circuit referred to as a type W309B. Bump and slope characteristics of the equalizer are set by a craftsman using switch settings. Currently, with the increasing use of digital electronic circuits in telephony for cost savings, it is desirable to implement the commonly used W309B equalizer in a digital circuit. Further, the availability of digital signal processor (DSP) integrated circuits would seem to facilitate this implementation. However, several problems are encountered which must be overcome to allow the DSP to be used to implement the type W309B equalizer. First, an earlier analysis of the W309B equalizer indicated that the switches set the gain and bandwidth characteristics of the filter. If this were the case, it would not be possible to implement the W309B equalizer on the DSP. Second, there are constraints on both the amount of memory available on the DSP and the size of numbers that can be stored in memory.